Coprime arrays are an example of a product array where both subarrays are sparse colinear ULAs [1]}, and the undersampling factors (USF) in the two subarrays must be coprime [1]}, [3]}, [4]}, [5]}. Fig. REF A depicts a coprime array where Subarray A and Subarray B have 14 and 21 sensors respectively, with USFs equal to 3 and 2 respectively.
